The present disclosure generally relates to a control circuit for a power converter and, more particularly, to the control circuit with a reduced number of package pins.
With the progress of the technology, electronic elements may be downsized to fit in the limited space of the electronic devices. For example, the integrated circuit (IC) element is frequently utilized in the electronic devices and comprises a die encapsulated by a package. The IC element usually needs to be coupled with many electronic elements through the package pins, and therefore a large-size package is usually needed for accommodating the required number of the package pins. In this situation, the die size is usually much smaller than the size of the package. Not only the wasted package materials result in environmental issues, but also the dimensions of the IC elements may not be reduced effectively.
In the field of power converters, e.g., AC to DC (AC-DC) power converters and DC to DC (DC-DC) power converter, when the control circuit of the power converter is realized with an IC element, the die size of the control circuit is usually small compared with the size of the package. The control circuit, however, needs a plurality of pins to be coupled with other circuit elements, to configure the power stage circuit of the power converter, to receive feedback signals, to receive operation parameters, etc. The package encapsulating the die of the control circuit must have enough pins, which are usually accompanied with the increase in the package size. The design flexibility is therefore constrained.
Some try to reduce the required pin numbers and the package size of the IC elements by utilizing one or more shared pins. Because the characteristics of IC elements are different, there are no clear principles which may be applicable universally. The circuits of the IC element sharing a shared pin must be carefully designed to ensure the correct functionality of the IC element.